1. Field of the Invention
The embodiments herein generally relate to patterning a semiconductor substrate and more particularly, the chemistries used in etching a boron doped hardmask layer.
2. Description of the Background Art
Reliably producing submicron and smaller features is one of the key requirements of very large scale integration (VLSI) and ultra large scale integration (ULSI) of semiconductor devices. However, with the continued miniaturization of circuit technology, the dimensions of the size and pitch of circuit features, such as interconnects, have placed additional demands on processing capabilities. The multilevel interconnects that lie at the heart of this technology require precise imaging and placement of high aspect ratio features, such as vias and other interconnects. Reliable formation of these interconnects is critical to further increases in device and interconnect density.
As device feature sizes become smaller, it has become increasingly more difficult to etch a pattern in the current conventional amorphous carbon hardmask layers without generating defects in the pattern lines formed therein. These pattern line defects in the hardmask layer make it difficult to deep etch high aspect ratio (HAR) features in the underlying dielectric layer while having a good line edge roughness (LER) under the sub 20 nm critical dimensions due to wiggling or roughening of the sidewall in the amorphous carbon hardmask layer.
Conventional hardmask layers include a carbonaceous layer, which consist of an inorganic material comprising at least 20% by weight carbon. Included in this class of materials is amorphous carbon (a-C), typically comprising greater than 50% by weight carbon. While some improvement in HAR etch performance is attained with such carbonaceous masking layers, even greater etch improvements may be provided in boron doped carbonaceous layers. The boron-doped amorphous carbon (a-C:B) results in a layer which has increased resistance to various etchants than previous amorphous carbon hardmask layers. However, the greater resistance of the boron doped carbon hardmask layer to the plasma etches processes call for aggressive etchants that result in poor vertical sidewall profiles when deep etching 20 nm, and smaller, critical dimensions.
Therefore, there is a need for an improved method for etching a boron doped carbon hardmask layers.